1. Field of the Invention
The present invention relates to an elongated, preferably an omnidirectional antenna, comprising an elongated rod-like structure, which is provided with a number of antenna elements located at two or more longitudinal positions. The invention also concerns a metal joint element for use in an antenna structure.
2. Description of the Related Art
Such antennas, especially omnidirectional antennas, being used today are often designed as a colinear arrangement of dipole antenna elements coupled in series to a transmission line. Although there is a general need for a high gain within a fairly wide frequency band, e.g. in a range of about 150 MHz to around 1900 MHz, the existing antennas of this kind only permit rather narrow frequency ranges with an acceptable gain, which is a disadvantage in cellular telephone systems.
There are also other known antennas having antenna elements being fed in parallel from a corresponding number of coaxial cables. Of course, such parallel feed cables will cause energy losses and increase the complexity and make the antennas more expensive.